Sunflower is generally cultivated for obtaining oil which has saturated fatty acids (palmitic and stearic) and unsaturated fatty acids (oleic and linoleic). The stearic acid content is always less than 10% (Gustone, F. D. et al. “The lipid handbook”; Chapman and Hall 1986), normally comprised between 3% and 7%. In relation with the unsaturated fatty acids there are two different kinds of sunflower seeds: the normal sunflower which has a linoleic acid content between 50% and 70% (Knowles, P. F. “Recent advances in oil crops breeding”; AOCS Proceedings 1988) and the high oleic sunflower which has 2–10% of linoleic acid and 75–90% of oleic acid (Soldatov, K. I. “Chemical mutagenesis in sunflower breeding”; Int. Proc. 7th Intern. Sunflower Conference, 352–357, 1976). There is also a sunflower line having a high palmitic acid content, between 22% and 40% (R. Ivanov et al. “Sunflower Breeding for High Palmitic Acid Content in the Oil; Proc. of the 12th Intern. Sunflower Conference, Vol. II, 453–465, 1988) and another line with low saturated fatty acid content (6% or less) (EP-496504).
Table 1 shows the fatty acid composition for some known sunflower oil varieties.
TABLE 1% of fatty acids in sunflower oilVarietyPalmiticStearicOleicLinoleicNormal15.95.721.866.5High oleic13.14.884.96.7Low saturated23.92.289.94.0High palmitic325.14.310.656.41Fernández Martínz et al.; Grasas y Aceites 37, (1986)2Patent EP-A-4965043This variety has also 3.6% of palmitoleic acid
The saturated fatty acid content of an oil is directly related with the physical and chemical characteristics thereof. In case that said content is sufficiently high, the oil can be a solid at room temperature like some animal fats. Normal sunflower oil is always a liquid under said conditions.
In the food industry like for the production of confectionery or margarine, animal fats or hydrogenated vegetable fats are usually used because a solid or semi-solid product is required. By means of hydrogenation unsaturated fatty acids are converted into saturated fatty acids. Animal fats as well as hydrogenated fats are not very recommendable from a nutritional point of view (chow, C. K. “Fatty acids in food and their health implications”, Dekker, N.Y., 1992). Animal fats have a relatively high cholesterol content. Too much cholesterol in the diet may be detrimental to the health. Therefore animal fats have been substituted in the last years by hydrogenated vegetable fats which do not contain cholesterol.
However, said hydrogenated fats present another problem derived from the hydrogenation process. In said process positional isomerization (shift of double bonds) and stereo-chemical transformations (formation of “trans” isomers) take place. Isomers are produced in an amount of up to 30%–50% of the total fatty acids amount. These isomers are not very healthy from a nutritional point of view (Wood, R., “Biological effects of geometrical and positional isomers of monounsaturated fatty acids in humans”; Dekker, N.Y. (1990); Willet, W. C. & Ascherio, A., “Trans Fatty Acids: Are The Effects Only Marginal?”, American Journal of Public Health, Vol. 84, 5, (1994)). Therefore, the use of hydrogenated fats in the food industry should be avoided.
Sunflower oil has a desirable content of unsaturated fatty acids. For use in the food industry however, the stearic acid content of the oil must be higher than in the normal sunflower oil (Norris, M. E., “Oil substitutions in food formulations”, Inform. 1, 388–392 (1990)) in order to obtain a more solid product.